A nitrogen-free etch stop layer is currently preferred for copper dual damascene structures having a low-k dielectric intermetal layer to avoid problems caused by outgassing from the low-k dielectric (e.g., via poisoning, resist scumming, via blinding). Currently a bi-layer structure is often used for providing a nitrogen-free etch stop layer for 90 nm and above technologies, for example. A SiOC layer is currently used as a nitrogen-free etch stop for the dual damascene process. SiOC is currently adopted for its low-k dielectric properties and inter-metal dielectric etch selectivity. A bottom SiC layer is currently used as a glue layer to improve the adhesion between the underlying layer and the etch stop layer. When part of the underlying layer includes copper (e.g., for metal interconnects and/or contacts), the SiC layer also prevents the SiOC from oxidizing the copper. However, a bi-layer structure often causes additional interface adhesion concerns, due in part to the current quality of the SiOC and SiC layers. Also, the use of and processing of the SiOC as the etch stop layer introduces the problem of oxidizing copper in the underlying layer. Thus, it would be desirable to be able to eliminate the bi-layer structure for nitrogen-free etch stop layers, as well as limiting or eliminating the use of SiOC as an etch stop layer material in some cases (e.g., 65 nm technology).